Passing C++ function parameters from QML

AndyPartridge

I wonder if anyone could help point me in the right direction with the following.

I am simply trying to call a C++ function from QML with the highlighted line of code (**)

@ Text {
width: parent.width
height: parent.height
horizontalAlignment: Text.AlignHCenter
verticalAlignment: Text.AlignVCenter

** text: xmlHandler.title(hexPosition)

    color: "#ffffff"
    font.pixelSize: 17
    font.family: gothamBlack.name
    font.capitalization: Font.AllUppercase
    wrapMode: Text.WordWrap
}

@

hexPosition is derived from the index of a Repeater - this is functioning just fine because hexPostion is used elsewhere.

xmlHandler.h contains:

@#ifndef XMLHANDLER_H
#define XMLHANDLER_H

#include <QObject>
#include <QString>

class XMLHandler : public QObject
{
Q_OBJECT
Q_PROPERTY(QString title READ title WRITE setTitle NOTIFY titleChanged)
Q_INVOKABLE QString title(const int index) const;

public:
void setTitle(const QString &title);

public slots:

signals:
void titleChanged();

private:
QString m_title;

};

#endif // XMLHANDLER_H@

xmlHandler.cpp contains:

#include "xmlhandler.h"

@void XMLHandler::setTitle(const QString &title) {
if ( title != m_title) {
m_title = title;
}
}

QString XMLHandler::title(const int index) const {
return QString("Base Handler");
}

@

main.cpp contains:

@
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QtQml>

#include "xmlhandler.h"

int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
XMLHandler xmlHandler;
QQmlApplicationEngine engine;
engine.rootContext()->setContextProperty("xmlHandler", &xmlHandler);
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
return app.exec();
}
@

I currently get the error:

@
/Users/Andrew/app/app_build/moc_xmlhandler.cpp:134: error: too few arguments to function call, single argument 'title' was not specified
case 0: reinterpret_cast< QString>(_v) = title(); break;
~~~~~ ^
@

I know that my "title" function currently does do anything with the index I am attempting to pass to it. I just want to make sure I can get it in the fore now!

Any help would be much appreciated.

SGaist

Hi and welcome to devnet,

It seems that you are mixing several not completely related things
This version should work better:

@
{
Q_OBJECT
Q_PROPERTY(QString title READ title WRITE setTitle NOTIFY titleChanged)

public:
Q_INVOKABLE QString title(int index) const; << before, it was private
QString title() const; << this one is for your property

public slots:
void setTitle(const QString &title);

signals:
void titleChanged(const QString&);

private:
QString m_title;

};
@

Hope it helps

AndyPartridge

SGaist, thank you for your help.

I have adjusted the header file as you suggest and have added the additional version of the title function, as:

@#include "xmlhandler.h"

void XMLHandler::setTitle(const QString &set_title)
{
if ( set_title != m_title) {
m_title = set_title;
}
}

QString XMLHandler::title(int index) const
{
return QString("Base Handler with Index");
}

QString XMLHandler::title() const
{
return QString("Base Handler");
}

@

I now receive an error stating "Property 'title' of object XML Handler is not a function.", from the QML file.

As you can tell, I have rather thrown myself in the deep-end here! But if you have any suggestions, it would be greatly appreciated.

AndyPartridge

Fortunately, I've sorted the problem I have mention above. The problem was this line:

@Q_PROPERTY(QString title READ title WRITE setTitle NOTIFY titleChanged)@

using 'title' for the QString and the READ - a big no-no!!

SGaist, I thank you again for you help - I continue my trek up the steep learning curve!

SGaist

What do you mean ? It's a standard Q_PROPERTY usage

AndyPartridge

Being somewhat of a novice with Qt, I am at a loss to fully explain as to why. But as described, the line:

@Q_PROPERTY(QString title READ title WRITE setTitle NOTIFY titleChanged)@

gave an error stating that the Property title is not a function. When I changed it to:

@Q_PROPERTY(QString title READ getTitle WRITE setTitle NOTIFY titleChanged)@

and adjusted the function name, the error vanished. No other parts of the code were changed.

I'm just reporting my experience with this, if I am attributing the error removal to the wrong piece of code, then I would be intrigued to know your thoughts on what it could me - it may help other noobs too!